244 STUDIES IN THE EVOLUTION OF ANIMALS 



of the same line of descent, or branches thereof, such as the 

 Rhinoceros, the Tapir, etc. 



In the Horse it is stated that all other digits have disappeared, 

 leaving only what are called the ' splint bones ' insignificant 

 remnants, or vestiges, which show that originally two other digits 

 were there. The big one only has remained, becoming bigger and 

 bigger by absorbing to itself the function of all the normal five 

 digits. Indeed, in the modern Shire stallion, the hoof is not unlike 

 a round dish-cover. 



In the Natural History Museum l there is arranged a very 

 pretty gradation of specimens, commencing from an ancient 

 extinct type, which has one big digit (the iii.) in the middle of four 

 smaller ones, and going up to the one solitary digit of the Horse. 



It has become a sort of dogma that the hand and foot of the 

 Horse are different from the hand and foot of the Ox ; the former 

 being, it is supposed, one enlarged digit, and the latter two dis- 

 tinct digits ; and further, that these two animals belong to two 

 different groups, the Horse belonging to the uneven-toed group 

 (Perissodactyls\ and the Pig, Ox, etc., to the even-toed group 

 (Artiodactyls). 



As so many professors of note have embraced and propounded 

 this theory, it might seem a bold sort of presumption on my part 

 to re-open the question, which has become the basis of an estab- 

 lished conviction among biologists. But facts, they say, are 

 stubborn things. I shall place before the reader certain facts, 

 which are my reason for re-opening this interesting question. 



In discussing a subject like this it is well to begin at the 

 beginning. In the Natural History Museum, gallery of fossils, 

 case 9 (c. d.), there is a cast of an extinct animal Pkcenacodus 

 primczvus (Eocene) not larger than a biggish Dog, with five digits 



1 Fossil Gallery, case 9. 



